Spa filter



FIG. 1 is a perspective view of a spa filter showing my new design;

FIG. 2 is a perspective view thereof, taken from a different angle;

FIG. 3 is a top elevational view thereof;

FIG. 4 is a side elevational view thereof; and

FIG. 5 is a side elevational view thereof, showing a different side. 

The ornamental design for a spa filter, as shown. 